This invention relates to a method of, and apparatus for, bonding a thermosensitive label to an object article to be labelled, the thermosensitive adhesive label being equipped on its back with a thermosensitive adhesive which exhibits tackiness upon heating and retains such for an extended period of time.
Conventional labels in general are coated with an adhesive which is constantly tacky, are then bonded to a peelable separate paper and are shaped in the form of a sheet or roll. The labels are peeled off from the separate paper one by one and bonded to object articles to be labelled. According to this method, however, the separate paper serves only as a bonding means, has no commercial utility, and is uneconomical because it increases the production cost of the label. Since the separate paper has a thickness which is equal to, or greater than, the thickness of the label, the label becomes bulky as a whole and is more difficult to handle. Moreover, the separate paper must be discarded in vain.
Thermosensitive adhesive labels have been proposed as labels which do not use the separate paper and solve the above-mentioned problems. However, because no separate paper is used, the label as a single sheet is difficult to hold or heat. A conventional mechanical method of bonding the label is illustrated in FIG. 1. A paper roll having the same width as an intended label is used as a label element 1. A desired length is fed out by a feed roller 3 upon the instruction of a detector 2 and is cut by a cutter 4. Thereafter, while the label is drawn and held on a vacuum drum 6 with the thermosensitive adhesive 9 facing upward, the label is passed in front of a heater 5 disposed adjacent to the vacuum drum 6. After the thermosensitive adhesive 9 becomes tacky upon heating by the heater 5, the label is bonded to an object article 8 to be labelled that is being conveyed by a conveyor belt 7.
However, in accordance with this method, the label 9 cut by the cutter 4 is heated by the heater 5 while it is held on the vacuum drum 6, so that a complicated mechanism is necessary to prevent the label 9 from falling off the vacuum drum 6. Moreover, the subsequent operation of bonding the label 9 to the object article 8 would be out of balance unless this suction and hold operation is well controlled, making this method difficult to practice. This method has another problem in that since the heater 5 for the thermosensitive adhesive 9' usually uses radiation heat, the heat efficiency is low and hence, a large capacity heat source must be used.
The present invention is primarily directed to eliminate these problems with the prior art. It is a first characterizing feature of the present invention that after the label cut to a desired length is placed on a heat-transferable conveyor belt which is being heated, the thermosensitive adhesive of the label is heated via the aforesaid conveyor belt so as to cause its tackiness and the label is then peeled off from the said conveyor belt by means of an acute turn and is thereafter bonded to the object article to be labelled.
It is a second characterizing feature of the present invention that in place of a system which directly heats the heat-transferable conveyor belt, heating means such as heaters are disposed on a travelling path of a conveyor belt which is resistant to degradation by heat for conveying the thermosensitive adhesive labels in order to simultaneously heat the thermosensitive adhesive labels and the conveyor belt.
It is an object of the present invention to provide both a novel and useful method and apparatus for labelling by the use of a thermosensitive adhesive label, and specifically the type of labels which do not use separate paper backing, but are instead coated on the back with a thermosensitive adhesive exhibiting tackiness upon heating; which apparatus and method obviate the use of vacuum devices for handling of the labels; which are reliable and advantageous in use; and which provide substantially greater heat efficiency; and which eliminate other problems of the prior art.